I, R2=LR 4, Nhu v~y mQt cau can bang la cau co:
b)d¢ng cd thu)'lIfC
tfnh thea each trcn do phl,l thuQc vao toc dQ t<!-i d6 kh6ng khf d!eh ehuyen piston. Cae h¢ thong khi nen luon c6 van de dieu chinh toc d<).
Kich - truy(jn d(mg quay: tip suat dong chat luu (dju ho~c khi) co th~ sir dl.!-ng de sinh chuy~n dQng tron. Hlnh 2.48 (a) the hi~n hieu do dan gian cua bQ kfeh truyen dqng quay kitfu d.nh g';lt. Ap suat chat lUll t~i duang vao lam quay eanh qui,lt. BAng vi?c t<;to chuyen dong quay lien tl,le khi sir dl.!-ng cae d.nh qU<;tt ehiu keo boi 10 xo keo co the t';lO ra dQng CC1 thuy Jl!e/khi nen nhu hlnh 2.48 b).
Bt) kich truyC-n dt)ng mim ngan la. d';lng kieh truy~n dQng pho thong clla h~
khf nell, gom mQt mang ngan mQt ben tin hi~u ap suat dau vao tiI bQ dieu khien va mOt ben tip suat moi lruang, ehenh l~eh clla hai ap suAt nay gQi la ap suat do
(gauge presure). SI! thay doi trong ap ll!c dau VaG gay chuycn d(>ng chi tiet trung tam giUa m~lllg
ngan (hinh 2.49). Chuyen d(>ng nay truyen tai tMnh phan dieu khien cu6i
thong qua tf'-!-e gan lien II
Ap sua! khi quyen L6 xo HJ b9 dl€U khien , I" ,~i~U khien ca p sua! khf quyen
vOi mung ngan. Ll!e tac Hinh 2.49: B(! kich truye'n d(mg mall ngon
dl,lng len tn;lC F bang tip ll/C do P(hien thi tren dong ho) nhan vai A, tiet di~n clla mang, tuc F=P.A. M~c khac, Il!e hoi duqc cap boi 10 xo. Nhu v~y, neu 10 xo dieh ehuyen mOt do~n x, thi Ilfc F tuang ling vai Il!c nen 10 xo: F = k.x (k -he so dan hoi eua 10 xo, gia tr~ kh6ng dai) . Suy fa kx=P.A.
Nhu v~y dich chuyin clla try.e ti I~ thu~n vai ap lW do
BO kich ~Iruyen dong mang ngil.n la 10':li kich truyen dOng tjnh tien do tin hi~u tiI hQ dieu khien duqe ehuyen thanh ehuyen d¢ng thang. Chuyen d¢ng thJng nay thuang duqe Slr dl.!-ng de' v~n hanh cae van dieu khitn qua tdnh.
Vall di(!u cMnli qua trinh khi nen thuang la thanh phan di~u khien cuoi, duqc kich dOng boi chuyen d¢ng eiia CC1 cau chap hanh h¢ kich truyen dong. Kct qua lu lUll luqng va toe dQ dong ra duqe quyet djnh boi hlnh d';lng phan nap- tMn van. Trang thl!e te cac van duqe su dl,lng kha pho thong, thea hlnh d~ng phfin dau bit thuang la mQt trong d.c kitu sau:
- Ma nhanh (quick opening), ('.10 thay doi toc dO dong 16n eho mOt dich chuy~n nh6 .
- Bien d;:.ll1g tuycn tinh (liniar-contoured), t<.to thay dbi toc dO dong ti I¢ vdi sl! thay doi dich chuycn phan dau bft.
- Phan tram b[mg nhau (equal percentage), t'!-o thay d6i dong thea phan tram bang veri. phan tram sl! thay d6i vj tei phan dau bit.
Trong thiet ke ho~c i,!a chQn kich thudc cua van, nguoi ta thuemg dung thu~t
ogiJ kich co van dieu khi~n qua trinh (procccs control valve size). D6 la kich cC1 than van dugc xac d~nh theo lUll luqng va toc dq dong, luqng giam ap qua van cho phep khi biet ti trQng cua chat lUll.
Hlnh 2.50 the hi?n SI! ket hQ'p cua van ong vdi mQt xilanh thuy ll!c , t'!-o thanh be} klwe'ch dgi thuy life. Van 6ng c6 ap suat cao- co dinh, chuy6n d6i hic dQng len cac m~t ben
cua xilanh (actuator) thea chuycn dQng dau vao cila trl,lc van ong . Ll!c tac dl,lng len xilanh Iii. tich elJa di¢n tich cong tac cua xilanh v6'i hi¢u cua ap suift cao va ap suat thoat [Fcr= A (F,,- FT)]. Ll!c nay cao hem
Hinh2.5I: D(Jng co Ihuy l!(c
nhieu so vai l,!c dich chuy6n trl,lc van Gng. Ket cau nay d ugc su dl,lng lam thanh phan dieu khi6n cu6i. de t;:to ll;fc Ian can thie't, djch chuyen phoi trong m(lt may cong CI,l. mnh
2.51 the hi?n vi¢c sii dl,log van Gog voi mQt
d(lng co piston hu6ug trl,lc t::t0 thanh mQt dqllg cd thuy life. Van ong cGng c6 the ho,!-t dQng nhu van die"u cldnh IHi/lllX.
2.4.3. He thong kich d(mg dien
H~ thong di¢n dugc sir d~ng nhu cae th1mh phan kich d¢ng thmJ'ng iii.:
• Thiet bi d6nglngat nhu cang tac Cct, diN. tiristo, tranzito, d do till hi¢u dicU'"
khien dllqc ap van fiN cong tac d~ dong ngat ffi¢t so thiet bi di¢n nha bQ
dot nong ho~c dQog ca.
• Thiel b~ lo~i s6len6it, (; do dong di~n qua cu¢o day dugc sir d~ng M kfch
d¢ng 16i day kim lo~i memo Vi d\l, sblen6it van thuy It,c/ khl nen sir dl,log dong di¢n qua seIenoit dt kich d¢ng lu6ng thuy It!c/khf nen. (adsbygoogle = window.adsbygoogle || []).push({});
• H¢ th6ng phat d¢og: vi dl,l, d¢ng cO DC ho~c AC, a do dong di¢n ch~y qua dQng co duqc dung de: sinh ra chuyin dQog quay.
2.4.3.1. Cae cong tac
C6ng tac thuemg g~p trong h¢ thong kich dQog di~n sir dl,lng d~ dong] ngat m~ch, d9ng cO di¢n, cae thanh phin dot nong, kich dQog cae van selen6it. dieu
khi~n d.c xilanh thuy h!c ho~c khi nen, ki~m soat mQt \o').t hanh d¢ng co tr~t tl!. Ho~t dQng chuy~n rn~ch co the Ia ket qua hO<;lt d9ng co h9c cua m9t bQ kich dQng di~n- co boi dong di~n trong s6len6it ho~c di¢n tii th6ng qua cac khoa di¢n tu (solid-state divice).
C6ng tdc C(/
C6ng tile Cd g6m 1 ho~c nhieu c~p tiep x.uc c6 th~ dugc dong ho~c rna co h9C M thl,fc hi¢n nail ngat m<;lch di~n. Cae c6ng tae IOi;li nay co th~ v~n hanh thu e6ng ho~c t1! dQng nha mllc chat long, nhi¢t dQ, dong chay, ap .<;uat, Mnh cam
ho~c nhGng thanh phan khac, tuc chung d6ng ho~c rna cac tiep diem ella minh
t~i nhUog gia tri tuang {mg cy the nao d6.
Cac rule
Role la thu~t ngiJ chi cac thiet bi chuyen m<;lch di¢n tll: bao gam: cac d6ng ngfit tiep diem (contaetors), cae
khoi d9ng d9ng CO (motor staters), role ht{n gia (time-delay relays). Role duqc Slr dl.J.ng trong nhUog Ung dl.J.ng khac nhau nhlffig thuang ho').t dQng thea cung nguyen H la cap nang IUQng cho nam cham di¢n M dong/rna ITlQt c6ng tac co. Role di~n cho phep
NguOIl,-_ _
_ _ _ _ :)~ <I
,
--, O~---.
J
ho~t d(mg ehuy~n m(~eh oan gian khi chip lIng mQt tin hieu dieu khien (hinh 2.52). Khi co dong di¢n ch<:J,Y qua eUQn day, xuit hi~n mQt tU truemg day tay don ehuy~n dQng bUQc cae tiep xuc phai ma ho~c dong.
Role hfn gi(f Ia iO<:Li dieu khi~n co th~ tri hoan mQt hO<:lt dQng chuyen m<:lch. Thai gian tri hoiin c6 th€ dieu ehlnh va dugc bat dau khi co dong di~n ch<:lY qua cUQn day hO~lC ~hi dong ngirng.
Khi lila chQn mN role, can phiii chu y cae tham so sau: • Di¢o ap ho~t dQng cu.a cUQo
• Cong suat danh dinh cua cu¢n day • Di¢n ap danh dinh
• Dong lam vi¢c
Khoa di~n til (solid-state switxhes)
MQl s6 chi tiet ban dan co th~ dung cho d.c m<:lch dong ngat di~n-di~n tu" Do lil diot, tiristo triac va tranzito.
Diot (den 2 c¥c) thuQc lo~i chuyen m<:lch di¢n tu cang suat (swiehing power electronics), diu t<:lo tit ban dan ket noi lO<:J,i p-n. CI!C noi phia mien p gQi la anod, cl!c n6i mien n gQi ta catod. Diot co duemg d~c tuye"n Von-Ampe th~ hi~n trong hlnh 2.53, Ia. duemg cong phuc t<:tP chia thanh 3 vUng sau:
(1)- vung phan cllc thu~n (vUng rna):
khi VIJ>VY (Vy=O,7V doi v6i silicon, O,3V doi v6i germanium), khi do diot dong, anod va catod tra thanh m<:teh tuang duang voi ngu6n di¢n rip nguqc ehieu Vy (hlnh 2.53).
(2)-vung phan cllc ngugc (vung khaa): khi V,<V n< Vy, luc do diot ho~t dqng nhu mqt m'.lch hb.
(3)- vung danh thung: khi v IJ<V IJ diot l<).i ho~t dQng l.,i nhu dong m<).ch, voi dong di¢n Ian qua diat.
e-j pin f--e : /D'"
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Hlnh 2.53: DtJc rinh clla di6t
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